Get the maximum TCP timeout in sessiond

This actually just open some /proc files when calling
lttcomm_init_inet() and computes the maximum value a TCP timeout for
every possible operations (send/recv/connect).

This is the first patch to fix the health check issue of having a
smaller delta than the TCP maximum possible timeout.

Signed-off-by: David Goulet <dgoulet@efficios.com>
Fix: set the health delta tcp timeout aware

The health check subsystem now initialized the time delta using the TCP
timeout. It takes the maximum value between our default internal delta
and the TCP timeout fetched by the lttcomm inet subsytem.

Signed-off-by: David Goulet <dgoulet@efficios.com>